Porous refractory diaphragm



Oct. 8, 1929. R. E. LowE 1,731,053

POROUS REFRACTORY DIAPHRAGM Ffiled May 51, 1925 W WW .Ww 45WWWWWWW W WWWWWWW N W-WWWW WWW W WwW-5W /WWWWWWWWW WWW W- W Wr WW# WWW WWWW W f W Patented ct. 8, 1929 UNITED STATES PATENT OFFICE RUSSELL E. LOWE, OF NEW YORK, N. Y., ASSIGNOIR- TO DOHERTY RESEARCH COMPANY, OF NEW YORK, N. Y., A CORPORATION F DELAWARE POROUS REFRACTORY DIALPHRAGM Application led May 31, 1928.

The present invention relates to gas burners l and more particularly to porous refractory diaphragms for the surface combustion of gaseous fuels.

lt has been proposed to force an explosive mixture of gas and air through a porous ref fractory diaphragm and to burn the explosive mixture in the outer layer of the diaphragm, causing the surface of the diaphragin to become incandescent but with substantially no ilame. An apparatus for burning explosive gaseous mixtures according to the method just mentioned is disclosed iu Patent 1,223,308 Bone et al.

It has been found that there is a tendency for the combustion to work inward into the refractory diaphragm. This tendency is objectionable, not only for the reason that it fic-creases the temperature and brightness of the outer or exposed surface of the diaphragin, but also because the high temperature zone is apt to work back suiiiciently far to ignite the gas at the inner or rear face of lthe diaphragm, thereby causing an explosion. Various devices have been proposed for preventing the retrograde movement of the zone of combustion just described and it has been found useful, among other expediente, to maintain the radiation from the outer surface of the diaphragm at as high a rate per square inch as possible. Among the expedients or devices previouslyT employed for producing a high rate of radiation from the outer surface of the diaphragm is that of forming parallel grooves and rid es on the outer surface of the diaphragm. t has been found, however, that diaphragms having ribbed surfaces, such as those just mentioned, soon crack when used for surface combustion.

It is the princi al object of the present invention to provi e a porous refractory dief phragm for surface combustion having a high rate of radiation and which is free from cracking and breaking from thermally produced stresses.

Serial No. 281,819.

The novel features of the present invention are pointed out in the appended claims. The invention itself, however, together with further objects and advantages, will best be understood from the following description taken in connection with the accompanying drawing in which: v

Fig. 1 is a cross section taken through a surface combustion burner apparatus having a porous rc fractory diaphragm according to the present invention;

Fig. 2 is a plan View of the diaphragm ili lust-rated in Fig. 1.

The thermal stresses in porous refractory diaphragnis used for surface combustion and provided with parallel grooves and ribs have always produced cracks extending transversely of the ribs. It has been found, according to the present invention, that the formation of thermally produced cracks in the surface combustion diaphragm can be avoided by forming the diaphragm with two sets of parallel webs or ribs, the webs or ribs of one set extending transversely to those of the other.

Referring to the drawing more in detail, is a porous diaphragm according .to the present invention. Diaphragm 10 is illustrated as mounted in a-casing 12, one face of the diaphragm being exposed to the atmosphere. The exposed face of diaphragm 10 is indented as indicated at 14, 14, the indentations 14 being spaced at their outer edges so that the diaphrao'm has ribs or webs 16, 16 and 18, 18 extending across its face between the indentations 14. Preferably the indentations 14 have the form of inverted pyramids and Hare outwardly toward the exposed face of the diaphragm. The webs 16, 16 run parallel forming one set of webs or ribs and the webs 18 also are parallel each to each, but extend transversely of thc webs or ribs 16. Preferably the Webs in the set numbered 16 run at right angles to those in the set numbered 18. Preferably the indentations 14 are made as small as can be satisfactorily molded so as to increase the radiating'surface of the diaphragm to the maximum. It has been found that pyramdal indentations having a square base of about one-fourth inch on the sideis the minimum size permitted by the present methods of molding known to the applicant.

'I he indentations preferably have an angle of 60 and therefore a depth of slightly less than onefourth inchl when they have square bases one-fourth inch on cach side. It will be understood that the ribs of the diaphragm are somewhat diagrammatic in Fig. 1, the depth of the indentations 14 bein exaggerated. It has been found that a 'aphragm eight inches square, two inches thick from the outer face of the ribs to the inner surface of the diaphragm and having square pyramidal indentations a little less than one-fourth inch deep and one-fourth inch on the side is suitable, when properly lcombined and molded, for a rate of gas feed of 250 cubic feet per hour. The rate of feed of as, of course, depends not onl on the thic ness of the diaphragm,'but a so on the gas pressure. In the example just given a gas pressure of ten inches of water is assumed. lith the same dia hragm, namely one two inches thick and eig t inches square, a rate of 360 cubic feet of gas per hour is attained at a gas pressure of sixteen inches of water. The amount of air used with the gas in the apparatus under discussion is such as to produce an explosive mixture and is preferably either exactl or close to the amount of air required for t eoretically complete combustion. An air-gas ratio of 5:1 is suitable when city as having a B. t. u. value of approximate y 550 per cubic foot is used.

The diaphragm, according to the present invention ma be of any suitable material and compounv ed and molded as desired within the limits of good practice. The prior patents to Bone, Wilson & McCourt Nos.

. 1,223,308; 1,223,248; and 1,223,249 contain directions for compounding and tiring porous diaphragms suitable for use in connection wit the present invention.

It is preferred, however, to use a porous refractory diaphragm formed in accordance with the invention disclosed in thel co-pending application of Messrs. Brown, Bjorkstedt and Lowe and according to which the diaphragm is formed principally of zircon (zirconium silicate), a Very refractory material and one highly resistant to the flow of heat. The zircon is preferably bonded with onehalf per cent of precipitated ferrie oxide, molded into briquettes, fired, crushed and screened, the greater per cent of the particles being of a. ineness of between 20 and 40 mesh and having a porosity of approximately 30 per cent. The porous particles just mentioned are then used to form the body of a porous diaphragm by mixing with approxii face design and baked at 140 to 180 F. to

remove water. lIn order to prevent the diaphra m from adherin to the mold, the mold shou d be painted wit flexible, collodion be fore the material is placed therein. Flexible collodion is'collodion containi about 2% of castor oil. Following removal m the mold the diaphragm is finished by firing to 2600"- 27 00 I* In the arrangement illustrated, the casing 12 is formed to rovidea gas chamber 20 at the rear of the iaphragm 10 and the losive mixture of air andgas is introduced into the chamber 20 through apipe 22. Air under suitable pressure may be introduced into pipe 22 through pipe 24 and gas under suitab e pressure may be introduced .into pipe 22 through pipe 26. Pipe 24 contains valve 28 and pipe 26 contains valve 30 whereby the amount of air and gas in the explosive mixture may be proportioned as desired. It will be noted also that a acking 32 is inserted between the edge of diaphr m 10 and the adjacent casing to prevent le age of gas between the diaphragm and casing.

Thile I have described a particular method of making a diaphragm, it will be understood that I do not limit myself to any particular method, but contemplate, within the present invention, all diaphragms having fine porestherein for the passage of gaseous mixtures and having an outer `indented surface, the surface identations being separated by two sets of webs and the webs of one set intersecting the webs of the other at an angle. Preferably, however, thegwebs of one set are parallel and cross those of the other set at right angles. Y

Having thus described my invention, what is claimed as new is:

l 1. A surface combustion apparatus comprising a porous diaphragm having indentations in its front surface and two sets of webs on said surface, the webs of one set crossing those of the other at an angle, a gas chamber at the rear of said diaphragm and means for introducing combustible gas and oxygen into said chamber.

2. A porous diaphragm refractory for the surface combustion of fluid fuel having indentations on one face and having two sets of webs on said face, the webs of one set crossinv those of the other at an angle.

Ei. A diaphragm as set forth in claim 2 and in which the indentations are of pyramidal p form.

4. A diaphragm as set forth in claim 2 and }3 in which the intersecting Webs form angles of degrees.

5. A porous refractor diaphragm for the surface combustion of uid fuel having pyramdal indentations in one face and having two sets of webs on said face, the webs of one set crossing those of the other at angles of 90 degrees.

6. A diaphragm as set forth in claim 2 and in which the Webs of each set are parallel and cross each other at an angle of 90 degrees.

In testimony whereof I affix my signature.

' RUSSELL E. LOWE. 

